A baking process is carried out as one of photolithographic processes, used for fabricating semiconductor integrated circuits. In a baking process, a semiconductor wafer is baked by using a baking oven.
A resist layer formed on a semiconductor is exposed with KrF light and developed to form a pre-designed resist pattern. After that, a high-temperature baking treatment is carried out on the wafer. A hot-plate type of baking oven has been used. The bottom surface of a wafer, which is arranged in the oven, is heated by a hot plate, while a purge gas is supplied into the oven. During such a process, the resist pattern is shunk. A resist pattern having a width narrower than 0.10 μm can be formed.
According to the above-described baking process, a change rate of size of a resist pattern is does not occur equally on the entire surface of the wafer. That is, the resist pattern is more narrowed at the center or inner portion of the wafer than around the peripheral edge or outer portion of the wafer. As a result, ICs or LSIs formed on the wafer may have different quality.